Conventionally, there has been proposed an LED lighting control device that relates to a lighting circuit of an LED luminaire with an LED element as a light source (e.g., JP 2011-171238 A (hereinafter, referred to as a “document 1”)). In the document 1, the LED luminaire using the above mentioned LED lighting control device is described.
The LED luminaire in the document 1, as shown in FIG. 17, includes an LED light emitting portion 51, as a light source, which is provided with LED elements, and a lighting circuit portion 52 which is configured to turn on the LED light emitting portion 51.
The lighting circuit portion 52 includes a filter circuit 53, a full-wave rectifier 56, a boosting chopper circuit 54 and a non-insulated type step-down chopper circuit 55. Note that, the document 1 discloses that the filter circuit 53 is provided with a fuse (not shown).
The boosting chopper circuit 54 includes a capacitor C51, a choke coil L52, a switching element Q52, a resistor R51, a diode D52 and a capacitor C53.
The step-down chopper circuit 55 includes a control circuit IC3, a diode D51, a switching element Q51, a choke coil L51 and a capacitor C52. The capacitor C52 is connected in parallel with the LED light emitting portion 51.
The lighting circuit portion 52 of the above-mentioned LED luminaire includes, as a step-down circuit, the non-insulated type step-down chopper circuit 55. Accordingly, in the above-mentioned lighting circuit portion 52, if for example a short-circuit failure occurs at the switching element Q51 in a lighting state of the LED light emitting portion 51, a voltage boosted by the boosting chopper circuit 54 is applied to the LED light emitting portion 51. For this reason, in the lighting circuit portion 52, an overcurrent Is may flow along a path indicated by a broken line with an arrow in FIG. 17. Furthermore, in the lighting circuit portion 52, when the overcurrent Is flows through the LED light emitting portion 51, the LED light emitting portion 51 may fall into an overloaded state.